Showing papers by "Erwin G. Van Meir published in 2022"
TL;DR: In this paper , RNA and/or DNA sequencing data from the temporally separated tumor pairs of 304 adult patients with isocitrate dehydrogenase (IDH)-wild-type and IDH-mutant glioma were analyzed.
90 citations
TL;DR: In this article , the core binding factor alpha (CBFA) complex was found to converge on the group 4 medulloblastoma (G4 MB) in the unipolar brush cell lineage.
Abstract: Medulloblastoma (MB) comprises a group of heterogeneous paediatric embryonal neoplasms of the hindbrain with strong links to early development of the hindbrain1–4. Mutations that activate Sonic hedgehog signalling lead to Sonic hedgehog MB in the upper rhombic lip (RL) granule cell lineage5–8. By contrast, mutations that activate WNT signalling lead to WNT MB in the lower RL9,10. However, little is known about the more commonly occurring group 4 (G4) MB, which is thought to arise in the unipolar brush cell lineage3,4. Here we demonstrate that somatic mutations that cause G4 MB converge on the core binding factor alpha (CBFA) complex and mutually exclusive alterations that affect CBFA2T2, CBFA2T3, PRDM6, UTX and OTX2. CBFA2T2 is expressed early in the progenitor cells of the cerebellar RL subventricular zone in Homo sapiens, and G4 MB transcriptionally resembles these progenitors but are stalled in developmental time. Knockdown of OTX2 in model systems relieves this differentiation blockade, which allows MB cells to spontaneously proceed along normal developmental differentiation trajectories. The specific nature of the split human RL, which is destined to generate most of the neurons in the human brain, and its high level of susceptible EOMES+KI67+ unipolar brush cell progenitor cells probably predisposes our species to the development of G4 MB. Derailed differentiation of human-specific progenitors of the developing cerebellar rhombic lip is the cause of group 4 medulloblastoma, the most common childhood brain tumour.
27 citations
TL;DR: In this paper , the effect of reduced expression of full length Bai1 on behavior, seizure susceptibility, and brain morphology in Adgrb1 mutant mice was studied, and the results showed that reduced levels of Bai1 is associated with a broader range of clinically relevant phenotypes than previously reported.
4 citations
1 citations
TL;DR: In this paper , BAI1/ADGRB1 was used to prevent MDM2 nuclear activity by trapping it at the cell surface, and in the process suppress tumor formation by stabilizing p53.
Abstract:
Medulloblastoma (MB) is the most aggressive pediatric brain tumor and a better understanding of this disease is warranted to develop new therapeutic approaches. Brain-specific Angiogenesis Inhibitor 1 (BAI1/ADGRB1) is an orphan seven-transmembrane G protein-coupled receptor predominantly expressed in the brain and epigenetically silenced in MB formation. MDM2 is an E3 ubiquitin ligase that leads to the proteosomal degradation of multiple proteins. We previously found that BAI1 can prevent MDM2 nuclear activity by trapping it at the cell surface, and in the process suppress tumor formation by stabilizing p53. Since MDM2 also ubiquitinates cell surface proteins, we hypothesized that its membrane trapping might increase the degradation of oncogenic tyrosine kinase receptors. To explore this idea, we examined IGF1R, a known cell surface MDM2 target and found that BAI1 negatively regulates IGF1R at the protein level. In contrast, BAI1 expression did not change the protein expression levels of other RTKs (INSR, EGFR). Using co-immunoprecipitation assays we confirmed that MDM2 interacts with both BAI1 and IGF1R in MB cells. In addition, the interaction between IGF1R and β-Arrestin, which is crucial for ubiquitination and down-regulation of IGF1R by acting as an adaptor for MDM2, was increased with BAI1 expression. To examine the impact of BAI1 overexpression on IGF1 receptor signaling, we examined its downstream signaling mediators (Stat3, Akt, Erk). Stat3 and Akt phosphorylation were suppressed upon BAI1 expression, while Erk signaling was activated but through a mechanism independent from IGF1R expression. As IGF1R is known to drive radiation resistance, we examined whether BAI1 could radiosensitize the cells and found that this was indeed the case. Altogether, our data indicate that reactivating BAI1 in MB has dual anti-tumor effects by stabilizing p53 and blocking IGF1R signalling.
TL;DR: This study deepens the understanding of adaptive resistance during repeated irradiation in GBM, and validates the IGF1/N-cadherin/b-catenin/Clusterin signaling axis as a novel target for radio-sensitization, which has direct therapeutic applicability.
Abstract:
Many subtypes of brain tumors are highly malignant and resistant to chemo- and radio- therapy. Tumor cells can shift their phenotype in response to treatments, the so-called adaptive resistance. Adaptive resistance mechanisms in malignant brain tumors are still poorly understood, and effective treatments have not yet been developed. To unveil such mechanisms, we have developed unique new experimental models to identify the adaptive resistance mechanisms to fractionated radiation in malignant brain tumors. We performed repeated irradiation (2-5Gy every 3-4 days, 3-6 weeks) on 6 human Glioma stem cells (GSCs), 2 mouse GSCs and 4 medulloblastomas (MB) cells in vitro and examined how tumor cells adapt to repeated irradiation. Brain tumor cells demonstrated dynamic adaptation to fractionated irradiation. They rapidly altered cell proliferation, intercellular adhesion, and stemness and acquired strong radioresistance. To identify genes responsible for radio-resistance, we performed RNA-seq analysis and CRISPR library screening using primary and radioresistant cells. We found that N-cadherin was upregulated in the majority of radioresistant GSCs. Stably transfecting N-cadherin in parental GSC rendered them radioresistant, reduced their proliferation, and increased their stemness and intercellular adhesive properties. Conversely, radioresistant GSCs lost their acquired phenotypes upon CRISPR/Cas9-mediated knockout of N-cadherin. Mechanistically, elevated N-cadherin expression resulted in the accumulation of b-catenin at the cell surface, which suppressed Wnt/b-catenin proliferative signaling, and reduced neural differentiation. Moreover, N-cadherin increased Clusterin secretion, which protected GSCs against apoptosis after radiation treatment. We also demonstrated that N-cadherin upregulation was induced by radiation-induced IGF1 secretion, which caused an EMT-like phenotype change in GSCs. The N-cadherin-mediated radioresistance phenotype could be reverted with picropodophyllin (PPP), a clinically applicable blood-brain-barrier permeable IGF1 receptor inhibitor. Adjuvant PPP combined with irradiation significantly extended the survival of orthotopically xenografted mice versus irradiation-only or drug-alone controls, supporting clinical translation. In conclusion, our data indicate that IGF1R inhibition can block the N-cadherin-mediated resistance pathway. Our study deepens our understanding of adaptive resistance during repeated irradiation in GBM, and validates the IGF1/N-cadherin/b-catenin/Clusterin signaling axis as a novel target for radio-sensitization, which has direct therapeutic applicability. These findings also confirmed that our radioresistant models effectively identify new adaptive resistance mechanisms in malignant brain tumors. (References: Osuka S, et. al., J Clin Invest. 2021;131(6):e136098)
Citation Format: Satoru Osuka, Dan Zhu, Zhaobin Zhang, Chaoxi Li, Christian T. Stackhouse, Oltea Sampetrean, Jeffrey J. Olson, G. Yancey Gillespie, Hideyuki Saya, Christopher D. Willey, Erwin G. Van Meir. N-cadherin is a driver of adaptive radioresistance in malignant brain tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1430.
TL;DR: In this paper , the N-terminal thrombospondin type 1 repeat (TSR#1) of BAI1 inhibits the maturation process of TGFβ1, a key growth factor involved in EMT.
Abstract:
Glioblastoma (GBM) is the most common and lethal type of malignant brain tumor in adults. GBM cells spread extensively in the brain and disseminate into the cerebrospinal fluid space, strongly restricting multimodal therapies. Acquiring a better knowledge of molecular defects underlying GBM invasion is essential for developing effective treatments.Brain-specific Angiogenesis Inhibitor 1 (BAI1/ADGRB1) is a transmembrane receptor of the adhesion GPCR family widely expressed in the normal brain, but its expression is lost in the majority of GBM through epigenetic silencing and restoration of its expression can inhibit glioma growth. However, whether BAI1 loss is important for tumor invasion and the mesenchymal phenotype in GBM has not been investigated.Microarray analysis of the GBM TCGA dataset (restricted to IDHwt GBM; WHO 2021) revealed that low BAI1 mRNA expression correlates with elevated expression of many mesenchymal genes. Restoration of BAI1 expression in human GBM cells suppresses mesenchymal gene expression in culture and dramatically decreases brain tumor invasion in mice xenografts. Mechanistically, we found that the N-terminal thrombospondin type 1 repeat (TSR#1) of BAI1 inhibits the maturation process of TGFβ1, a key growth factor involved in EMT. BAI1 is silenced epigenetically in GBM cells by methylated CpG-binding protein MBD2, and its expression can be reactivated by KCC-07, a blood-brain barrier permeable MBD2 inhibitor. We found that restoration of BAI1 expression by KCC-07 treatment dramatically suppresses cell invasion in the brain and reduces leptomeningeal dissemination of GBM cells to the spine in mouse xenografts.These experiments demonstrate that epigenetic silencing of BAI1 is important for activating the GBM invasive phenotype through TGFβ1 pathway activation. This new tumor-suppressive pathway can be epigenetically targeted to reactivate BAI1 expression in GBM patients.
TL;DR: Recurrence-associated changes in genetics and the microenvironment that can be targeted to shape disease progression following initial diagnosis are uncovered.
Abstract:
Diffuse glioma is characterized by a poor prognosis and a universal resistance to therapy, though the evolutionary processes behind this resistance remain unclear. The Glioma Longitudinal Analysis (GLASS) Consortium has previously demonstrated that therapy-induced selective pressures shape the genetic evolution of glioma in a stochastic manner. However, single-cell studies have revealed that malignant glioma cells are highly plastic and transition their cell state in response to diverse challenges, including changes in the microenvironment and the administration of standard-of-care therapy. To interrogate the factors driving therapy resistance in diffuse glioma, we collected and analyzed RNA- and/or DNA-sequencing data from temporally separated tumor pairs of over 300 adult patients with IDH-wild-type or IDH-mutant glioma. In a subset of these tumor pairs, we additionally performed multiplex immunofluorescence to capture the spatial relationship between tumor cells and their microenvironment. Recurrent tumors exhibited diverse changes that were attributable to changes in histological features, somatic alterations, and microenvironment interactions. IDH-wild-type tumors overall were more invasive at recurrence and exhibited increased expression of neuronal signaling programs that reflected a possible role for neuronal interactions in promoting glioma progression. In contrast, recurrent IDH-mutant tumors exhibited a significant increase in proliferative expression programs that correlated with discrete genetic changes. Hypermutation and acquired CDKN2A homozygous deletions associated with an increase in proliferating stem-like malignant cells at recurrence in both glioma subtypes, reflecting active tumor expansion. A transition to the mesenchymal phenotype was associated with the presence of a specific myeloid cell state defined by unique ligand-receptor interactions with malignant cells, providing opportunities to target this transition through therapy. Collectively, our results uncover recurrence-associated changes in genetics and the microenvironment that can be targeted to shape disease progression following initial diagnosis.
Citation Format: Frederick S. Varn, Kevin C. Johnson, Jan Martinek, Jason T. Huse, MacLean P. Nasrallah, Pieter Wesseling, Lee A. Cooper, Tathiane M. Malta, Taylor E. Wade, Thais S. Sabedot, Daniel J. Brat, Peter V. Gould, Adelheid Wöehrer, Kenneth Aldape, Azzam Ismail, Floris P. Barthel, Hoon Kim, Emre Kocakavuk, Nazia Ahmed, Kieron White, Santhosh Sivajothi, Indrani Datta, Jill S. Barnholtz-Sloan, Spyridon Bakas, Fulvio D'Angelo, Hui K. Gan, Luciano Garofano, Mustafa Khasraw, Simona Migliozzi, D. Ryan Ormond, Sun Ha Paek, Erwin G. Van Meir, Annemiek M. Walenkamp, Colin Watts, Michael Weller, Tobias Weiss, Karolina Palucka, Lucy F. Stead, Laila M. Poisson, Houtan Noushmehr, Antonio Iavarone, Roel G. Verhaak, The GLASS Consortium. Longitudinal analysis of diffuse glioma reveals cell state dynamics at recurrence associated with changes in genetics and the microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2168.
TL;DR: In this article , the authors showed that hypoxia-induced transcription factors (HIFs) increase the expression of genes that promote tumor growth (e.g., metabolic adaptation and invasion/metastasis).
Abstract:
New treatment approaches are urgently needed for children with medulloblastoma (MB) to augment survival and reduce the long-term side effects from the treatment. Malignant tumors often display hypoxic regions where hypoxia-induced transcription factors (HIFs) increase the expression of genes that promote tumor growth (e.g., metabolic adaptation and invasion/metastasis). Based on the known roles of HIF in many solid tumors, we hypothesized that Hypoxia/HIFs contribute to MB cell growth and targeting HIF proteins is a viable strategy for treating MB. To test our hypothesis, first, we exposed MB cell lines (ONS-76; Shh and D556; Group 3) to 1% hypoxia in cell culture. We found increased expression of both HIF1a and HIF2a proteins and activation of a hypoxia-response element driven luciferase reporter assay. Treatment of the cells with 64B, an arylsulfonamide HIF inhibitor abrogated reporter activity and reduced expression of hypoxia-induced genes (GLUT-1, VEGF). Next, we used CRISPR/Cas9 to knockout singly or in combination HIF1a/HIF2a genes. The inhibition of HIF reporter activity by 64B was partially canceled in single HIF-KO cells and completely canceled in double HIFs-KO cells, showing both isoforms were active. Second, to investigate HIFs can be therapeutic targets, we established orthotopic human MB xenografts in mice. We first examined the tumor for the presence of hypoxic areas and used pimonidazole (Hypoxyprobe) injections followed by immunohistochemistry and found hypoxic areas throughout the tumors where tumor cells expressed HIF1a and/or HIF2a. Evaluation of human MB samples for HIF1/2 expression is also ongoing. Next, we plan on injecting mice with cells devoid of HIFs genes and examine their growth. We will also treat the mice with 64B to test whether it has anti-tumor effects and extends survival. In conclusion, these results indicate that HIF activation is part of the pathobiology of MB and HIF proteins may be a target for MB treatment.